1. Field of the Invention
This invention relates generally to injection molding. In particular, this invention pertains to manifold and nozzle assembly constructions for facilitating assembly of mold components comprising a mold assembly.
2. Description of Related Art
It is known to provide injection molding equipment comprising constructions of a manifold and associated nozzle assemblies wherein nozzle assemblies are attached to a material distributing manifold to facilitate installation of the manifold and nozzle assembly in a mold assembly. As is known, components of a mold assembly include members to receive a manifold and members to receive at least a portion of at least one nozzle assembly and that further comprise a mold die element that defines at least a portion of a mold cavity. FIGS. 1a and 1b illustrate an example of a manifold and nozzle assembly construction and portions of a mold component in which such constructions are installed. Considering FIG. 1b, plates MP1 and MP2 define a space in which a manifold block MB, comprising manifold and nozzle assembly construction MNA (FIG. 1a), is received. A mold retainer plate MP3 supports a mold die block MD comprising at least a portion of a mold cavity such as cavity space MC. Each nozzle assembly, such as nozzle assemblies NA1 and NA2, is partially received in a recess such as nozzle well WN in a mold die block such as mold die block MD.
Continuing with reference to FIGS. 1a and 1b, nozzle assemblies NA1 and NA2 are retained with manifold block MB by threaded retainers such as retaining nut RN1 (FIG. 1b). Retaining nut RN1 is at least partially received in nozzle receiving bore MR of manifold block MB and retains nozzle assembly NA1 so that sealing contact is achieved between the inlet end of nozzle assembly NA1 and the ceiling of receiving bore MR. Desired sealing contact of the nozzle inlet end face with the ceiling of nozzle receiving bore MR is achieved by compressive forces exerted by the threaded connection of retaining nut RN1 with manifold block MB. As shown in FIG. 1b, a passage PM within manifold block MB is in fluid communication with a nozzle passage PN (shown in phantom (dashed lines)) through a nozzle assembly NA1. The outlet of nozzle passage PN is in fluid communication with mold cavity space MC through an opening (so-called “gate” MG) in mold die block MD. In manifold and nozzle assembly constructions comprising more than one nozzle assembly, a connecting passage, such as passage PC, conveys material from manifold passage PM to nozzle passage PN. Nozzle assemblies such as nozzle assembly NA1 advantageously comprise tip elements such as nozzle tip member NT having a passage there-through in fluid communication with nozzle passage PN and from which material exits the nozzle assembly. Sealing contact is made between nozzle assembly NA1 and nozzle well WN proximate the nozzle tip to prevent material from exiting the mold die block through nozzle well WN.
It is to be understood that flowable condition of material within manifold block MB and nozzle assembly NA1 is achieved by maintaining manifold block MB and nozzle assembly NA1 at suitably elevated temperatures. To that end, heating elements may be provided such as nozzle heater NH surrounding the elongated shank of nozzle assembly NA1. Likewise, heating elements may be provided in manifold block MB. Heat transfer from manifold block MB and nozzle assembly NA1 to surrounding members is reduced by minimizing contact therebetween. Hence, manifold block MB is supported between plates MP1 and MP2 with spacers (not shown) and nozzle assembly NA1 is spaced apart from sidewalls of nozzle well WN by precisely locating nozzle receiving bores MR in manifold block MB.
Sealing contact between nozzle assembly NA1 and mold members is dependent, at least in part, on alignment of nozzle assembly NA1 relative to the mold members. In particular, substantial parallelism between the face of the nozzle end surrounding the nozzle inlet and the ceiling of receiving bore MR surrounding the outlet of connecting passage PC is effective to maintain sealing contact therebetween when nozzle assembly NA1 is abutted to the ceiling of receiving bore MR. Likewise, desired sealing contact between nozzle assembly NA1 and nozzle well WN is achieved by abutment of an element of the nozzle assembly, such as a nozzle flange NF. Provided the longitudinal centerline of nozzle assembly NA1 is substantially parallel to the longitudinal centerline of nozzle well WN, sealing contact between nozzle flange NF and the sidewall of nozzle well WN will be realized.
As indicated, an advantage of manifold and nozzle assembly constructions illustrated in FIGS. 1a and 1b is that they are susceptible of pre-assembly to facilitate installation in mold components. A disadvantage of such constructions arises in consequence of thermal expansion in use that can result in forces that tend to cause tilting of nozzle assemblies relative to other mold component members. By virtue of deliberate thermal isolation of manifold and nozzle assembly construction MNA, manifold block MB will undergo different thermal expansion than other members of the mold component as temperature of the mold component is raised to a desired operating temperature. Considering the arrangement illustrated in FIG. 1b, it will be understood that by virtue of attachment of nozzle assembly NA1 to manifold block MB by retaining nut RN1, nozzle assembly NA1 is fixed in position relative to manifold block MB. Furthermore, by virtue of contact of nozzle sealing flange NF with the sidewall of nozzle well WN, nozzle assembly NA1 is fixed in position relative to mold die bock MD. Under circumstances where thermal expansion of manifold block MB effects a change of position of receiving bore MR, (the change of position being illustrated in phantom (dashed lines) in FIG. 1b) a transverse force EF is applied to the inlet end of nozzle assembly NA1. Unless there is a corresponding change of position of nozzle well WN, a corresponding force will not be applied to nozzle sealing flange NF. Consequently, nozzle assembly NA1 is subjected to a moment (unequal forces applied to points on opposite sides of the longitudinal center of the nozzle assembly) that tends to tilt nozzle assembly NA1 relative to the longitudinal centerlines of manifold receiving bore MR and of nozzle well WN, such tilt being represented by angles AA and BB, respectively, of FIG. 1b. Such tilt can result in loss of sealing contact between nozzle assembly NA1 and one or both of manifold block MB and nozzle well WN.
In constructions where the extent of thermal expansion driven tilting of nozzle assemblies relative to other mold members can so impair sealing contact that operation is adversely affected, it is known to arrange the manifold and associated nozzle assemblies to permit relative movement therebetween. Such known arrangements rely on abutting contact of the inlet end face of a nozzle assembly with an opposed face of a manifold block so that the manifold block can slide relative to the nozzle assembly while desired sealing contact is maintained. Compressive force holds the nozzle assembly in abutting contact with the manifold block so as to maintain sealing contact under normal operating pressure of material being conveyed from the manifold to the nozzle. The compressive forces are achieved by means that engage only the nozzle assemblies or manifold block rather than by means engaging both the nozzle assemblies and the manifold. A disadvantage of such known constructions arises from the lack of attachment of nozzle assemblies with manifolds negating pre-assembly of such constructions to facilitate installation of the construction in a mold assembly. Hence, there remains a need to provide manifold and nozzle assembly constructions that allow for pre-assembly thereof to facilitate installation in mold members and that permit relative movement of nozzle assemblies and the associated manifold in use.